Why ‘No Mow May’ could be a boon for Toronto’s bumble bee populations

Organizers say doing so will help introduce much-needed biodiversity and more native flowering plants, both of which are sorely lacking but essential for healthy urban bee populations.

“The sheer quantity of flowers and nectar production on lawns mown once a month can be astonishing,” said Trevor Dines, a botanical specialist at the conservation charity Plantlife, based in the U.K.

Plantlife, which is spearheading the initiative, says mowing your lawn just once a month can lead to a 10-fold increase in the number of bees pollinating the area.

The argument is backed up by a 2019 paper published by scientists at the Université du Québec à Trois-Rivières, which found that “intensively managed” lawns have been shown to have “clear negative ecological effects,” especially in urban areas.

And while Torontonians with more time on their hands might be itching to do some yard work as the weather improves, local conservationists say wildlife would indeed benefit from a more widespread “no mow” philosophy.

“Trying to increase the diversity of your lawn is actually a great idea because it really is one of the largest areas of vegetation that’s within most of our urban areas,” said Dan Kraus, a senior conservation biologist at the Nature Conservancy of Canada.

Kraus said reduced mowing, fertilization and irrigation could eventually help introduce helpful native species, such as wild strawberries, wild blue violets and trout lilies to more Toronto-area lawns.

The Nature Conservancy of Canada has previously led campaigns to stop people raking leaves in the fall, for similar biodiversity purposes.

“If you imagine dozens and dozens of backyards doing things to improve habitat for native pollinators, migratory birds, this could actually have a big impact on the quality and the diversity of our urban ecosystem,” Kraus added.

Toronto’s bees declining or disappearing

There’s hope that a wider availability of native flowering plants could help local bee populations recover after what has been a decades-long decline for some species.

“Sadly probably about at least a third of our species have disappeared or drastically declined,” said Victoria MacPhail, an environmental studies PhD student at York University who specializes in bumble bees.

MacPhail helps run the citizen science project Bumble Bee Watch, where people around Canada can submit photos of bees to help scientists learn more about local populations.

She listed several species that were once common but are now rarely seen, if ever, in the Toronto area. The list includes the yellow-banded bumblebee, American bumblebee, yellow bumblebee and cuckoo bumblebee.

The rusty patched bumble bee, once among the top-five most common species, has essentially disappeared from the region.

“It used to be in Toronto, you used to be able to walk outside your door and see it and now you can’t,” MacPhail said.

While MacPhail acknowledged the critical role that homeowners can play in revitalizing some of those species, she added that truly helping bee populations will require more than just letting the grass get long.

“I really encourage people, if they want to help pollinators, to actually create habitat for them,” she said.

Toronto residents without their own backyards can also help local bees through the city’s PollinateTO program, which awards $5,000 grants to help people create pollinator-friendly gardens in their neighbourhoods.